Feature
After Exercising, Eat Your Protein
April 5, 2007
Soy protein is fine to get muscles rebuilding after endurance work, IU researcher reports
IU School of Medicine–Evansville scientist Tracy Anthony says either plant or animal protein is good in your post-workout snack.
It's generally accepted nowadays that eating some protein, not just carbohydrates, will help your body start building and repairing muscle after strenuous exercise.
But does the type of protein you eat matter? To answer this question, Tracy Anthony, an assistant professor of biochemistry and molecular biology at the IU School of Medicine, put a contingent of rats through some serious exercise and came up with some surprising findings.
In a recent article in the Journal of Nutrition, Anthony and her colleagues at IUSM–Evansville compared whey, which is derived from cow's milk, to soy protein, a vegetable protein, on measures of muscle recovery after endurance exercise. They report that soy and whey perform comparably as a post–workout supplement, both increasing the production of new proteins in skeletal muscle.
Soy products are gaining popularity in the U.S. for their cardiovascular and other claimed health benefits. Yet some assume soy is an inferior protein source because it comes from a plant. Most plant proteins are low in one or more 'essential' amino acids, meaning those we must consume in our diet. Soy protein, however is a complete protein, containing all the essential amino acids needed for healthy growth, Anthony said. Animal proteins such as those in cow's milk also are complete proteins.
Anthony's recent findings are potentially important for those who maintain a vegetarian lifestyle and exercise regularly. Consuming soy protein after exercise can benefit their muscles too, she said. Her research may also alleviate the concerns of some male athletes who have previously resisted soy protein because soy products contain isoflavones (estrogen-like compounds) which were thought to be potentially feminizing, Anthony said.
Anthony's interest in the subject goes back about a decade when she was a graduate student at the University of Illinois. She investigated what was then a controversy over whether long distance runners and other "endurance" exercisers should add protein to their post workout snacks, which then focused mainly on carbohydrates.
After the body undergoes significant endurance exercise, protein production in the muscles is depressed, resulting in a "catabolic" state. Anthony wondered what happened if one ate protein, in addition to carbohydrates, afterwards.
It turned out that consuming protein did matter. Those rats that ate protein along with carbohydrates after exercising had significantly higher levels of protein production one hour later.
"It doesn't have to be a lot of protein. We used very small meals with these animals," she said — equivalent to having a serving of yogurt.
Anthony used a similar model for the recent "soy versus whey" experiment: Male rats were trained to exercise on a treadmill, reaching a level roughly equivalent to a human running a marathon. After exercising the rats were fed either a soy plus carbohydrate protein meal, a whey plus carbohydrate protein meal or a carbohydrate-only meal. They then were given a dose of a labeled amino acid, which enabled Anthony and her team to determine how much of the amino acid had been taken up into the muscles and used to make new proteins.
The analysis showed that both types of protein meals led to equivalent levels of protein production, and both produced more than the carbohydrate meal alone.
The next research step is to test whether the reported effects vary over longer periods of time, and in what ways, Anthony said. Understanding those variables could lead to development of an optimal supplement that would have a longer-lasting effect, something that could be particularly beneficial for older exercisers. Along these lines, Anthony wants to conduct additional research to see if the benefits of the protein consumption differ with age — the rats used in the studies were young.
